Model 33 wiring complexity

Shoppa, Tim tshoppa at
Wed May 10 12:22:02 CDT 2017

The Model 33's I bought back when I was a teenager, were all ex-Telex use and had exceedingly complicated wiring harnesses as well as built-in modems. They had paper tape readers and punches with various auto-start/auto-stop relay options.

The exceedingly complex wiring harnesses were to add various options. The wiring harnesses made the wiring of the unit look, literally, a thousand times more complex than it actually was.

In the end all I ever did was find the magnet wire, and the keyboard contact wire, for the main unit and the punch.

I usually also found a useful current loop supply in the base. Sometimes I would find bipolar relays and 20mA/60mA conversion supplies. I was a little surprised at some of the current loop supplies - some of them weighed 20 pounds and were obviously made for driving exceedingly long lines (open-circuit voltage way over 100VDC). Seemed odd these were in there considering the units had modems just a foot away from magnet and keyboard switch.

Tim N3QE

More information about the cctalk mailing list